<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .div1{
            float: left;
        }
    </style>
</head>
<body>

<div>我是第一行|</div>
<div class="div1">我是第二行|</div>
<div>我是第3行|</div>
<div>我是第4行|</div>
</body>
</html>